Ceratina cyanea

Ceratina cyanea can reach a length of 5–9 millimetres (0.20–0.35 in) (females) and 5–7 millimetres (0.20–0.28 in) (males).^[5] Head, chest and abdomen show a metallic blue colour.^[5][7] These bees have three submarginal cells in forewings,^[8] club-shaped antennae^[5] and a long thin tongue.^[5] The scutellum is densely punctured. The seventh tergite has a deep saddle and ends in two points.^[3][9]

The blue carpenter bees fly from mid-March to mid-October,^[5] collecting pollen at various families of plants, especially knapweed (Centaurea), yellow composites (Asteraceae) and Lotus (Fabaceae).^[6]

Females dig the nest extracting the soft tissue that fills the cavities of the vertical or slanted dry plant stems and small branches,^[7][6] such as thistles, blackberries (Rubus species),^[7] elderberries (Sambucus species) and roses.^[5][7] Then they provide the cells with a mixture of regurgitated nectar and pollen to feed the larvae.^[5] Adult males and females overwinter inside their cells into the stems. Often several insects spend the winter together.^[5]